54 votes

Is revving the engine to redline on idle at morning bad?

If your engine even has a problem carboning up, you don't clear it at cold start. Nor do you clear it by spinning the engine to redline. "Revving" isn't meaningful to diesel engine performance the ...
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47 votes
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Is revving the engine to redline on idle at morning bad?

Yes, this may be bad. The oil is not yet at the operating temperature, and the same is true for engine parts as well. I wouldn't redline a cold engine with cold oil. Your intention to clear carbon ...
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  • 13.7k
27 votes

What does O/D mean on a dashboard & a button under the transmission button?

As others have noted, the O/D button is used to disable and enable the overdrive gear. What hasn't been discussed is why you might want to use this button, and in what circumstances. The vehicle you ...
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  • 682
25 votes
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What does O/D mean on a dashboard & a button under the transmission button?

The "OD" means over drive. It's the last gear in your transmission. When the indicator shows as "off", it means the transmission won't go into that gear. Overdrive provides a mechanical advantage for ...
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14 votes
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How to find out if my non-fuel injected car has a rev limiter?

I'm not entirely sure a rev limiter will help protect you if you downshift at a speed higher than the gear you've selected is intended for. If you manage to lift the clutch, even without any fuel, ...
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13 votes
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Why doesn't my rev limiter bounce?

Traditional rev limiters work by controlling the ignition and/or fuel. Ignition Control Retarding the spark (smoother) Completely cutting the spark (more aggressive) Fuel Control - Amount ...
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  • 2,186
12 votes
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What happens to a car engine when giving max throttle while not in gear

The RPMs would certainly increase but the mechanical components would be prevented from exceeding maximum RPMs by a rev-limiter. Rev-limiters are built into the ECU (computer) of the car. When an ...
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  • 32.8k
10 votes

What happens to a car engine when giving max throttle while not in gear

While most new electronically controlled vehicles probably do have a rev-limiter built in, this doesn't mean you cannot go past the red-line of the engine. The red-line is the theoretical maximum you ...
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6 votes
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What actually happens when the engine approaches redline and the rev-limiter is reached?

Not intended to be a great answer but just so you know the information is there... From the description of the rev-limiter tag: Device used in the ignition system to limit the rotations per minute ...
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4 votes
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Engine revs to 4000 RPM without pressing gas pedal

I'm betting your Jag is Drive-By-Wire (DBW), meaning, there isn't a direct connection between you and the throttle. If so, the gas pedal rheostat is probably telling the computer you are pressing it, ...
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4 votes

What does O/D mean on a dashboard & a button under the transmission button?

As @Paulster2 explains it is overdrive. The reason you have a button to disable it is that there are situations where you need more torque, like pulling a trailer or carrying a heavy load. Overdrive ...
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  • 14.6k
3 votes

2007 Camry won't rev past the redline

Given you say "I'm pretty sure that it went past the redline before" I am going to assume that you aren't sure it ever did it. Cars are not only not designed from the factory to exceed the redline, ...
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3 votes
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How do I know if car ECU has a REV Limiter?

Rev limiter is a bit of a misnomer since maximum engine RPM is a function of airflow. However there are such things as fuel and spark cut off which will disable either injectors or coil packs as a ...
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  • 10.7k
2 votes

How to find out if my non-fuel injected car has a rev limiter?

I would expect a mass market car from the 1990s to have a rev limiter of some sort. But...as other posters have stated a rev limiter won't prevent over revving due to downshifting. Having said that ...
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  • 1,586
2 votes

How to find out if my non-fuel injected car has a rev limiter?

As stated by Steve, downshifting when the vehicle speed is too high for the gear selected will over-rev any engine. The rev limiter only stops the engine going too fast under its own power. Non-...
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2 votes
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Car not accelerating and over revving

Based on your description and assuming you have a manual tranmission car, it looks like your clutch is worn out and slipping. Driving like this with an over-revving engine and a slipping clutch will ...
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  • 1,350
2 votes

Do rev limiters like the Bee-R Rev Limiter cause any wear on engine components?

I'll admit that I don't have experience with these rev limiters, and I'm drawing conclusions from other experience. That said... On cars with catalytic converters in the exhaust, when the engine ...
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  • 13.2k
2 votes
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Does free revving diesel engine near redline for 2-3 seconds harm it

You are being overly paranoid. While this action isn't good for the engine, it won't harm it. There's a redline for a reason, that being an engine speed you should not exceed. You weren't exceeding ...
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1 vote
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Honda rev-limited at 4k RPM, automatic transmission won't shift into 5th gear, no CEL

For those who come after me... The issue ended up being a blocked catalytic converter. Holding it up to the light it looked fine, you could see easily through the honeycomb. What ends up happening is ...
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1 vote

Is revving the engine to redline on idle at morning bad?

Please no; don't do that. Use something like "Shell Rotella" with the proper detergents and let the oil do the work - over a long drive. I'm not sure what oil your owner's manual specifies, but use ...
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  • 12.3k
1 vote

Why would my car be dropping in revs when in gear?

Every automatic drops in rev´s a little, when in "drive". The torque-converter adds some load to the engine. It should not stall though - if it does, there is either something wrong with your motors ...
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  • 1,062
1 vote

Why won't my '05 VW Caddy rev past 3500rpm?

P0726 fault code can be caused by: A failed engine input speed sensor A failed transmission output speed sensor A short or open in the wiring harness to one of the sensors A loose connection to one ...
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  • 1,544
1 vote

Do rev limiters like the Bee-R Rev Limiter cause any wear on engine components?

The limiter does not cause any damage. How you use the limiter, and how often you wind the engine to said limit is a completely different question. As a generality, it is not going to be ...
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